In modern coating units for the series coating of construction parts, pig scrapers are used in order to remove coating agent from coating agent conduits. Coating agent residues, which stick to the inside wall of coating agent conduits, must be removed after coating operations. For example, the coating unit can be a paint unit for an automotive assembly line. A first set of automotive parts can be painted a first color by the coating unit. A second set of automotive parts can be painted a second color by the coating unit after the pig scraper has removed the first paint residue from the coating agent conduits of the coating unit.
A pig scraper is disclosed in EP 0405075B1, which consists of a basic body which can be inserted into a coating agent conduit. The basic body includes a sealing lip which essentially extends radially from the basic body and is located on a jacket surface of the basic body. During operation, the sealing lip fits tightly against the inside wall of the coating agent conduit to be cleaned. The pig scraper scrapes off coating residue sticking to the inside wall of the coating agent conduit and this way builds up an axial isolation path.
One disadvantage of pig scrapers currently known in the art is that the sealing lip can fold over in the axial direction of the body of the pig scraper when the direction of movement of the pig scraper is changed. When the lip of the pig scraper folds over, a portion of the lip is subjected to excessive deformation forces. As a result, the life of the pig scraper is shortened.